From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH 3/6] macvtap: zerocopy: validate vector length before pinning user pages Date: Mon, 16 Apr 2012 10:58:31 +0300 Message-ID: <20120416075831.GA9920@redhat.com> References: <20120416060749.14140.19433.stgit@intel-e5620-16-2.englab.nay.redhat.com> <20120416060807.14140.96229.stgit@intel-e5620-16-2.englab.nay.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org, xma@us.ibm.com, davem@davemloft.net, linux-kernel@vger.kernel.org, ebiederm@xmission.com To: Jason Wang Return-path: Content-Disposition: inline In-Reply-To: <20120416060807.14140.96229.stgit@intel-e5620-16-2.englab.nay.redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Mon, Apr 16, 2012 at 02:08:07PM +0800, Jason Wang wrote: > Currently we do not validate the vector length before calling > get_user_pages_fast(), host stack would be easily overflowed by > malicious guest driver who give us a descriptor with length greater > than MAX_SKB_FRAGS. Solve this problem by checking the free entries > before trying to pin user pages. > > Signed-off-by: Jason Wang We could handle this by copying and linearising some fragments. That would be better. > --- > drivers/net/macvtap.c | 2 ++ > 1 files changed, 2 insertions(+), 0 deletions(-) > > diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c > index 7cb2684..d197a78 100644 > --- a/drivers/net/macvtap.c > +++ b/drivers/net/macvtap.c > @@ -529,6 +529,8 @@ static int zerocopy_sg_from_iovec(struct sk_buff *skb, const struct iovec *from, > } > base = (unsigned long)from->iov_base + offset; > size = ((base & ~PAGE_MASK) + len + ~PAGE_MASK) >> PAGE_SHIFT; > + if (i + size >= MAX_SKB_FRAGS) > + return -EFAULT; > num_pages = get_user_pages_fast(base, size, 0, &page[i]); > if ((num_pages != size) || > (num_pages > MAX_SKB_FRAGS - skb_shinfo(skb)->nr_frags))